如何设置session?

比如，1.jsp,2.jsp错在那里？
1.jsp:<%@ page contentType="text/html; charset=gb2312" %>
<html><form name = "1" action="2.jsp" method = post>
<%
HttpSession session;
session.setAttribute("aa","1");%>
<table><tr>
<td align=center><input type="text" name="text" value=""></td>
</tr>
<tr><td align = center><input type="submit" name="submit" ></tr>
</table>
</html>
--------------------------------------------------------------------------
2.jsp<%@ page contentType="text/html; charset=gb2312" %>
<html>
<% HttpSession session = request.getSession();
String s = session.getId();

String a = (String)(session.getAttribute("aa")); %> <table><tr>
<td align=center><input type="text" name="text" value = s></td>
</tr>
</table>

</html>

解决方案 »

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给你一个完整的例子，一共有两个文件：login.jsp、Loginservlet.java，估计格式有点乱，
不好意思。
代码：
1.login.jsp
   <HTML>
   <HEAD>
   </HEAD>
   <BODY>
   <center>
   <form name='form1' method='post' action='/servlet/Loginservlet'>
   <br>
   <table width="300" border="1" cellspacing="0" cellpadding="0" height="22"
       bordercolor="#003333" align=center>
   <tr>
       <td bgcolor="#003333" height="18">
       <div align="center"><font color="#FFFFFF" class="white">登录</font></div>
       </td>
   </tr>
   </table>   <table width="300" border="1" cellspacing="0" cellpadding="0"
       bordercolor="#003333" height="129">
   <tr>
   <td>
       <div align="center">
       <table width="159" border="0" cellspacing="0" cellpadding="0">
       <tr>
          <td width="67" height="33">
    <div     align="center" class="item" nowrap>登入用户名：</div>
</td>
          <td width="92" height="33">
    <input type="text" id="username" name="username" size="12"
                                               style="FONT-SIZE: 9pt">
</td>
       </tr>
          <tr>
             <td width="67">
             <div align="center" class="item"  nowrap>密<font
                              color="#FFFFFF">....</font>码：
             </div>
    </td>
    <td width="92">
             <input type="password" name="password" size="12"
                                     style="FONT-SIZE: 9pt">
    </td>
</tr>
       </table>
       <table width="167" border="0" cellspacing="0" cellpadding="0">
<tr>
    <td>
    <div align="center"><br>
    <input type="submit" name="Submit" value="登入系统" >
    </div>
    </td>
</tr>
<tr><td> </td></tr>
       </table>
       <br>
       </div>
       </td>
       </tr>
    </form>
</center>
</BODY>
</HTML>
<SCRIPT LANGUAGE=javascript>

</SCRIPT>2.Loginservlet.java/*引入包文件*/
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
import java.util.*;public class Loginservlet extends HttpServlet
{
    public void doPost(HttpServletRequest req,HttpServletResponse resp)
    throws ServletException,java.io.IOException
    {
        String sDBDriver="oracle.jdbc.driver.OracleDriver";
        Connection conn=null;
        ResultSet rs=null;
        Statement stmt=null;
        PrintWriter out;
        String strUserName="",strPassword="",strPrompt="",strSQL="",strTemp="";
        boolean fAuthorized=false;
        int i=2;
        HttpSession session=req.getSession();
        out = resp.getWriter();
        try{
  Class.forName(sDBDriver);
        }catch(java.lang.ClassNotFoundException e){
  System.err.println("dbbean():  "+e.getMessage());
        }

        try{
  conn=DriverManager.getConnection
           ("jdbc:oracle:thin:@lmz:1521:labora","scott","tiger");
  stmt=conn.createStatement();
        }catch(SQLException e){}
  /**get parameter**/
  strUserName=req.getParameter("username");
  strPassword=req.getParameter("password");

  //instance session variable：
  session.putValue("login_name","");
  session.putValue("user_name","");           //Authenticate()
       strSQL = "select login_name,user_pwd from sys_user where
                    login_name='"+strUserName+"'";
  try{
      rs=stmt.executeQuery(strSQL);
      if(rs.next()){
fAuthorized=true;
                  rs.close();
               }else{
fAuthorized=false;
rs.close();
      }
               conn.close();
      stmt.close();
  }catch(SQLException e){
     out.println("数据库错误！"+e.getMessage()+"\n");
     out.println(strUserName);
     System.err.println("executeQuery():  "+e.getMessage());
  }       if(fAuthorized){
  strTemp=(String)session.getValue("login_name");
  if (strTemp.compareTo("super")!=0){
      strSQL = "insert into sys_log
               (user_name,prg_id,optype,primary,value,computer,ip) values('"+
      strUserName+"','00000','登录成功','登录名','"+
      session.getValue("user_name")+"','"+req.getRemoteHost()+
      "','"+req.getRemoteAddr()+"')";       try{
int iReturn=stmt.executeUpdate(strSQL);
      }catch(SQLException e){}
      }       if (((String)session.getValue("login_name")).compareTo("super")
                                                                        ==0)
                  {
     //resp.sendRedirect("/jsp/xxx.html");
      }else{//登录失败！
         strPrompt="登录失败，请重新登录。";
strSQL = "insert into sys_log
                  (user_name,prg_id,optype,primary,value,computer,ip) values('"
                       +strUserName+"','00000','登录失败','登录名','"+
(String)session.getValue("user_name")+"','"+
                  req.getRemoteHost()+"','"+req.getRemoteAddr()+"')"; try{stmt.executeUpdate(strSQL);}
    catch(SQLException e){}
    resp.sendRedirect("/login.jsp");
}
}
jsp里面不用这种东东 HttpSession session;
session直接用就可以了
还有我比较喜欢用session.getValue("XXX"),session.putValue("XXX")百试百灵
对,我在jsp中也不用  "HttpSession session",
一般用session.getValue(),session.putValue("",)都行!
在jsp不用HttpSession，但在servlet里面用HttpSession